Fully interpenetrating polymer networks (IPN's) and semi-interpenetrating polymer networks (“semi-IPN's”) have been created from a variety of starting materials and have been used for a variety of applications. IPN's and semi-IPN's can combine the beneficial properties of the polymers from which they are made and can avoid some of the undesirable properties of their component polymers.
Prior IPN's and semi-IPN's have been proposed for use in biomedical applications, such as a coating for an implant or as artificial cartilage. See, e.g., U.S. Patent Publ. No. 2005/0147685; U.S. Patent Publ. No. 2009/0035344; and U.S. Patent Publ. No. 2009/008846. The utility of prior IPN's and semi-IPN's for their proposed applications is limited by the properties of those compositions, however. In addition, the starting materials and processes of making such prior compositions limit not only the resulting properties of the IPN or semi-IPN but also the commercial viability of the manufacturing processes and the articles made in such processes. Also, the mechanical properties of prior IPNs and semi-IPNs are often limited by the mechanical properties of the component polymers used, which in the case of most intrinsically hydrophilic, water-swellable polymers, are usually quite low. For example, the prior art has not described a viable process for making a water-swellable IPN or semi-IPN from commercially available hydrophobic thermoset or thermoplastic polymers, such as polyurethane or ABS.
Finally, the utility of prior IPN and semi-IPN compositions and the value of the articles formed from such compositions have been limited by the inability to create IPN's and semi-IPN's with desired characteristics, such as strength, lubricity and wear-resistance.